1. Field of the Invention
The present invention relates to polymers resulting from polymerizing ethylenically unsaturated esters derived from 3,4-epoxy-1-butene or epoxybutene. The polymers may be homopolymers or copolymers containing other ethylenically unsaturated monomers. The polymers of the invention may be used in a variety of coating compositions such as inks, adhesives, paints, and films.
2. Description of the Related Art
The ring opening chemistry of epoxides is well known. (Evans et al., J. Chem. Soc. 248 (1949)). Opening an epoxide ring with a nucleophile can create one hydroxyl moiety or, depending on reaction conditions, two hydroxyl moieties. The hydroxyl groups can undergo further reaction. The hydroxyl groups can, for example, be converted to esters by reaction with carboxylic acids. Hydroxyl groups can also be converted to acetoacetic esters. (Clemens, R. J., Chemical Reviews, 86:241-318 (1986); Witzeman, J. S., U.S. Pat. No. 5,051,529 (1991)).
Reacting an epoxide group with an acid anhydride can yield a disubstituted ester derivative (U.S. Pat. No. 5,623,086). Reacting an epoxide with an alcohol results in the formation of a hydroxy ether and is well known in the literature. The remaining hydroxyl group may be further derivatized using, for example, carboxylic acids or anhydrides to form esters using methods well known to those skilled in the art.
The ring opening reaction of 3,4-epoxy-1-butene or epoxybutene with hydroxide base yields an ethylenically unsaturated diol, 3-butene-1,2-diol, having the following structure: ##STR2## The two hydroxyl moieties provide a possible means by which further functionality may be added to the polymer. For example, U.S. Pat. No. 2,504,082 describes the synthesis of the propenyl ester of 1-hydroxy-2-methoxy-3-butene. U.S. Pat. No. 4,916,255 describes the synthesis of the methacrylate ester of 1-hydroxy-2-methoxy-3-butene.
However, the polymerization of ethylenically unsaturated esters such as allyl esters has proven difficult. Homopolymerization of allyl esters such as allyl acetate is sluggish and results in a low molecular weight polymer. Allyl esters will also only copolymerize with a few selected unsaturated monomers such as vinyl esters or maleic anhydride. (C. E. Schildknecht, Allyl Compounds and Their Polymers, Wiley-Interscience, 1973).
Similarly, only a few monomers are known that will copolymerize effectively with vinyl esters. For a number of applications, particularly coatings, poly(vinyl acetate) needs to be modified with other monomers to provide a lower glass transition temperature, T.sub.g. Vinyl esters such as vinyl neodecanoate have been shown to be useful in lowering the T.sub.g of poly(vinyl acetate), but are expensive. Other vinyl esters that have also been shown useful in reducing the T.sub.g of poly(vinyl acetate) include butyl acrylate and 2-ethyl hexyl acrylate. Copolymers of vinyl acetate and butyl acrylate are heterogeneous due to the differences in reactivity (e.g., C. Pichot, M. F. Llauro, Q. T. Pham, J. Polym. Sci.: Polym. Chem. Ed., 19, 2619-2633 (1981)). However, monomers that will copolymerize well with vinyl esters such as vinyl acetate and result in polymers with functional groups available for post-polymerization are not known in the art.
Therefore, a need exists in the art for functionalized ethylenically unsaturated esters which may be used as monomers and undergo facile polymerization. Moreover, the needed monomers should not only be able to form high molecular weight polymers but also be able to copolymerize with a variety of other ethylenically unsaturated monomers. It would also be desirable that such a functionalized ethylenically unsaturated monomer contain functionality capable of surviving polymerization and undergoing further post-polymerization reaction.